1. Field of the Invention
The present invention relates generally to fluid delivery devices. More particularly, the invention concerns an improved apparatus for ambulatory infusion of medicinal agents into a patient at specific rates over extended periods of time.
2. Discussion of the Invention
Many medicinal agents require an intravenous route for administration thus bypassing the digestive system and precluding degradation by the catalytic enzymes in the digestive tract and the liver. The use of more potent medications at elevated concentrations has also increased the need for accuracy in controlling the delivery of such drugs. The delivery device, while not an active pharmacologic agent, may enhance the activity of the drug by mediating its therapeutic effectiveness. Certain classes of new pharmacologic agents possess a very narrow range of therapeutic effectiveness, for instance, too small a dose results in no effect, while too great a dose results in toxic reaction.
In the past, prolonged infusion of fluids has generally been accomplished using gravity flow methods, which typically involve the use of intravenous administration sets and the familiar bottle or bag suspended above the patient. Such methods are cumbersome, imprecise and require bed confinement of the patient. Periodic monitoring of the apparatus by the nurse or doctor is required to detect malfunctions of the infusion apparatus and to control flow rate.
Devices from which liquid is expelled from a relatively thick-walled bladder by internal stresses within the distended bladder are well-known in the prior art. Such bladder, or "balloon" type, devices are described in U.S. Pat. No. 3,469,578, issued to Bierman and in U.S. Pat. No. 4,318,400, issued to Perry.
The prior art bladder type infusion devices are not without drawbacks. Generally, because of the very nature of bladder or "balloon" configuration, the devices are unwieldly and are difficult and expensive to manufacture and use. Further, the devices are somewhat unreliable and their fluid discharge rates are frequently imprecise and operate over a wide flow rate tolerance.
The apparatus of the present invention overcomes many of the drawbacks of the prior art by eliminating the bladder and making use of recently developed elastomeric membranes and new high performance engineering materials, which, in cooperation with a plate-like, yieldably deformable base define a fluid chamber that contains the fluid which is to be dispensed. Until the device is used, the elastomeric membrane is in a substantially relaxed state. However, movement of the yieldably deformable base from a first configuration, such as a concave configuration, into a second configuration, such as a convex configuration, imparts internal stresses to the elastomeric film membrane in a manner to cause the membrane to tend to move toward its starting configuration thereby controllably forcing fluid contained within the chamber into fluid flow channels provided in the base and then outwardly to the patient through a fluid outlet port in communication with the fluid chamber. In one form of the apparatus of the invention, a thin, planar shaped fluid interaction member, which may be a filter or a flow control member, is strategically located within the chamber to controllably act upon the fluid flowing toward the fluid flow channels.
The use of state of the art thin membranes and films permits the construction of compact, low profile, laminated structures which are easy to use and inexpensive to manufacture. When the devices of the invention are to be used with ambulatory patients they are constructed of light-weight flexible materials so that the device can be carried by the patient.
The apparatus of the invention can be used with minimal professional assistance in an alternate health care environment, such as the home. By way of example, devices of the invention can be used for the continuous infusion of antibiotics, hormones, steroids, anti-blood clotting agents, blood and blood components, blood substitutes analgesics, parenteral agents, enteralnasogastric feeding and delivery of other medical agents. Similarly, the devices can be used for extended I-V micro infusion such as chemotherapy and KVO (keep vein open) and can accurately deliver fluids to the patient in precisely the correct quantities and at extended microfusion rates over time.